Fluid cooled electric discharge device



June 15, 1943. D. D. HINMAN 2,321,673

FLUID COOLED ELECTRIC DISCHARGE DEVICE I Filed March 28, 1941 /z i J InvenTov: D naLd D. Hinman,

Patented June 15, 1943 UNITED STATES PATENT OFFICE I FLUID cootsn gg c rgrc mscnaaon Donald D. Hinman, Cleveland Heights, Ohio, as signal to General Electric Company, a corporation of New York Application March 28, 1941, Serial No. 385,721

.More particularly it relates to an improved method for cooling such devices whereby a greater power output may be obtained without softening of the envelope walls and without disturbing the desired distribution of "mercury vapor in the envelope. The invention consists a stream of air onto the surface ofthe envelop" is provided. The air blastmay be supplied w r airunder pressure by any suitable source (no vided, the end section in the new and novel arrangement of. elements u hereinafter described and claimed.

In order to obtain very high luminous intensities such as are necessary in photographic 'pro- "j'ection work, for example, it is necessary to operate lamps of the above mentioned type at currents and voltages which produce high temperatures when concentrated within the relatively narrow confines of the lamp. It is generally necessary, therefore, to provide some means for artificially cooling the envelope in order to prevent softening thereof. In someeases, however, the cooling may also result in excessive cooling of certain portions, such as the end chambers, and consequently in an undesirable lowering of the mercury pressure. I have found that this defect can be eliminated by providing shielding means around the said end chambers in the manner hereinafter set forth.

It is, accordingly, an object of my invention to provide an artificially cooled lamp of the aforesaid type which shall be capable of withstanding greater energy concentration, and which shall be less subject to condensation of the metallic vapor in the end chambers thereof.

Further objects and advantages of the invention will be apparent from the following detailed description and from the accompanying drawing, the single figure of which shows a lamp constructed in accordance with the invention along with a circuit for operating the same.

Referring to the figure, the lamp I comprises an envelope 2 having therein an anode 3 and a cathode 4, as well as a quantity of metallic vapor such as mercury at pressures above about a quarter of an atmosphere during operation. In addition, a starting gas may be added at pressures up to several millimeters. The amount of mercury introduced will be such that at the normal operating temperature of the lamp the vapor atmosphere is unsaturated with mercury. The latter procedure is described in the Pirani, et al. application Serial No. 609,547, filed May 5, 1932. The lamp will be arranged to opcrate at currents above about 2 amperes, which that the 5 Claims. (01. 176-124) results in considerable heating. In order to prevent softening of the envelope under the effect of this heating-an air blast 5 arranged to direct;

shown). I have found, however, that unless shielding means such as shields 6 and l are-pro v surrounding the elec-"T' trodes become excessively.1,cooled,with the result bers.

members 8 provided with end portions 9' having re-entrant sleeve portions 9 which fit snugly over' the envelope. These members may be of any suitable metal or insulating construction. They may be also-of glass or quartz and made integral with the envelope. The effect of these end shields is to protect the end portions of the lamp from excessive cooling by the air blast 5 and thereby to raise the temperature of the said end chambers. In order to further raise the temperature, a coating I 0- of metal such as platinum may be provided for the purpose of reflecting back into the envelope any heat radiation whichtends to leave the end chamber. Alternatively, the caps ll may be provided on the shield members 8 for the purpose of cutting down the end radiation. The brass ferrules I! may be provided as extemal' terminals for the lamp and may be cemented thereto by any suitable means.

For the purpose of energizing the lamp, I have shown a source of direct current l3 connected in series with a ballast resistor I 4, a switch l5 and the lamp itself. In one case, this generator had a terminal'voltage of about 240 volts, while the resistor M was about ohms. Under .these conditions, approximately 2 amperes flowed through the lamp and the volt age between the electrodes wasabout volts.

For the purpose of completeness, the following dimensions of the aforedescribed lamp system mercury.conden;se'sfin the end cham- P The end shields may comprise cylindrical a lamp operated with alternating current, it would be well to position both of these portions 9 from 1 to 2 millimeters ahead of the tip of the corresponding electrode. The electrodes 3 and 4 were formed by winding tungsten wire of about 20 mils diameter loosely around; a piece of thorium and a core comprising a 25 mil tungsten wire. Each of such coils was approximately 6 mm. long. The cathodes may, however, be of the unactivated type described and claimed in the copending application of Lyman B. Johnson,

Serial No. 381,633, filed March 4, 1941.

It will be understood that many modifications in the described details of my invention may occur to those skilled in the art to which it appertains. For example, while Ihave stressed its use in connection with a' lamp having an unsaturated mercury vapor pressure, it may also mercury. means for supplying to said device an energy loading suiiicient to soften the envelope in the absence of vigorous artificial cooling, means for directing a concentrated compressed air-blast at said envelope substantially midway between said electrodes at a pressure suflicient to maintain the envelope at a temperature below be used with the saturated vapor type, i. e., the

type wherein the electrodes are formed by pools .of mercury. Further, it will beunderstood that the invention is equally applicable to lamps of the alternating current type, although I have shown it in connection with a direct current lamp. All such modifications I aim to include in the scope of the appended claims.

What I' claim as new and desire to secure by its softening point, and tubular shield members surrounding said electrode chambers and having closed front ends located closely adjacent to the tips of the said electrodes to prevent cooling of said end chambers by said air'blast with re-. sultant condensation of mercury in said end chambers.

2. The combination set forth in claim 1 wherein the amount of mercury in the envelope is insufficient to saturate the atmosphere therein at the normal operating temperature of the device.

3. The combination set forth inclaim 1 wherein the front ends of the shield members have reentrant sleeve portions extending rearwardly and fitting the envelope closely.

4. The combination set forth in claim 1 wherein the energy supply means includes a source of direct current and the front end of the shield member surrounding the cathode electrode is located a short distance ahead of the tip of that electrode while the front end of the shield member surrounding the anode electrode is located at-the tip of that electrode.

5. The combination set forth in claim 1 wherein the energy supply means includes a source of alternating current and the front ends of the shield members are located a short distance ahead of the tips of the contiguous electrodes.

DONALD D. HINMAN. 

